Devices for injecting a medication into a body or for aspirating a fluid, such as blood, from a body of a human or animal patient are well known. Such a device commonly includes a syringe barrel which can retain a quantity of medication or other injectant, and an intravenous or subcutaneous needle which is inserted into the skin of the patient for administration of a medication or aspiration of a fluid. These devices are generally of the disposable nature and hence are normally discarded after a single use.
It is common practice after the administration of an injection or the aspiration of fluids from a patient in which a conventional syringe is used for the user to replace a molded sheath or scabbard on the exposed contaminated needle to prevent inadvertent puncture wounds from the needle point, or to merely lay the syringe down upon a surface leaving the contaminated needle exposed. Replacement of the needle sheath is dangerous as such sheaths tend to be small in diameter thus requiring a concentrated effort to align the point of the needle with the opening of the sheath prior to sliding the sheath over the needle. Such occurrences often result in a person being inadvertently pricked or stuck by the contaminated needle.
Injury by accidental needle sticks has been recognized as a serious health hazard and the danger of exposure to fatal blood-transmitted viruses, such as hepatitis, herpes, and of must recent concern, acquired immunodeficiency syndrome (AIDS), through accidental pricks by a contaminated injection needle is well documented. Medical research has confirmed that the slightest prick or puncture of the skin by a contaminated needle may communicate the contaminating virus to the injured party. In addition, the syringe is normally discarded after a single use and if the contaminated needle remains exposed, this danger of exposure is likewise presented to those handling and disposing of the medical refuse.
One approach to this problem has been to provide a tubular cover or sleeve that can be slid downwardly over the needle after its use to shield the needle and prevent inadvertent contact therewith. Such prior attempts include syringe devices having a slidable sheath or sleeve member mounted thereon adapted to reciprocably and axially move over the syringe barrel and engaging means by which the sheath or sleeve may be fixed in a desired position. For example, a common embodiment of such an assembly includes a fixed guide lug which travels within a longitudinal slot or groove formed in the sheath so that the sheath can be moved to selectively cover or expose the needle. Examples of such inventions are presented in the following U.S. Pat. Nos.: 4,425,150 to Sampson, et al.; 4,643,199 to Jennings, Jr., et al.; 4,643,200 to Jennings, Jr.; 4,693,708 to Wanderer, et al.; and 4,702,738 and 4,723,943 to Spencer.
U.S. Pat. No. 4,743,233 to Schneider presents another prior attempt which provides a safety cap syringe generally comprising a safety sleeve mounted adjacent the syringe barrel and which extends axially to shroud the needle. In one embodiment of Schneider, the threaded barrel is provided with a threaded portion formed at its external surface adjacent the needle and the safety sleeve is provided with a pair of corresponding threaded portions formed at its internal surface, one threaded portion arranged adjacent the proximal end of the sleeve and the other adjacent the distal end. When the protective sleeve is moved to the closed or extended position, the proximal threaded portion of the sleeve threadably engages the threaded portion formed on the syringe barrel to releasably secure the safety sleeve in the extended position. By rotating the sleeve, the sleeve may be disengaged from the syringe barrel threads and thereafter slidably moved along the syringe barrel to expose the needle, at which point the sleeve is rotated again to threadably engage the distal threaded portion of the sleeve with the threaded portion provided on the syringe barrel, thereby releasably securing the safety sleeve in the open position so that the syringe is ready for use. Schneider provides no means, however, by which the safety sleeve may be permanently secured in the extended position. Such a feature is essential in preventing reuse of the contaminated needle and inadvertent puncture wounds caused by an exposed needle.
Furthermore, the absence of a permanent locking means in Schneider can prove hazardous as medical personnel often will not take or do not have sufficient time to screw the safety shield completely into position. For example, in emergency situations, a medical personnel may simply rotate the safety shield only a few rotations to engage the corresponding threaded portions, thereby making it possible during subsequent handling and jostling for the safety shield to become disengaged and move axially over the syringe barrel, thereby exposing the contaminated needle and representing the dangerous hazard.
Moreover, the safety sleeve and the pair of like threaded portions provided by Schneider are manufactured as an integral component of the safety-cap syringe. This arrangement complicates the manufacturing process involved as well as increasing its cost.
There has developed a definite need for a practical, inexpensive and simple solution to the problem of inadvertent injuries caused by contaminated needles during the handling of hypodermic syringe devices.